The long range-aim of this research is to analyze the molecular mechanism of human disorders involving aberrant DNA metabolism. The specific aims of this proposal encompass encompass several projects designed to examine in detail the etiology of systemic lupus erythematosus (SLE), in relation to DNA metabolism; aberrant antigen DNA production and aberrant antibody production. We have established a new method to isolate DNA fragments from DNA/anti-DNA antibody immune complexes (DNA immune complexes) from sera of patients with active SLE. We have identified two classes of DNA fragments from DNA immune complexes; the small fragment with 40 base pairs and the large fragment with 150 base pairs. Both of them originate from nuclear DNA of SLE patients and are rich in guanine-cytosine residues. We plan now to amplify these DNA fragments by molecular cloning in order to look for general sequences which might be the antigenic and/or recognition sites for anti-DNA antibody; to correlate the amounts of DNA bound to DNA immune complexes with disease symptoms; to analyze nuclear DNA breakage in SLE patients and to look for factors responsible for DNA damage; and to examine how methylation of nuclear DNA varies with disease symptoms. The methods and concepts developed with this system will be applied to other human disorders involving aberrant DNA metabolism, or chromosome instability syndromes and cancer. By focussing on DNA damage, repair and methylation, I hope to gain new insight into the etiology of these diseases.